Cenote Sagrodo:The Serpent's Maw

A historian, Ethan, along with two sisters—geologist Chloe and photojournalist Maya—explore a mysterious sinkhole in Mexico's Yucatán Peninsula known as the Cenote Sagrado. They discover a vast subterranean world built by an ancient, intelligent civilization and uncover a terrifying, millennia-spanning secret that threatens the very survival of humankind.(I will be posting this story on RoyaRoad as well)